Our long-term study on the quantitative at-sea distribution of the upper trophic levels – seabirds and marine mammals – in polar ecosystems aims at quantifying the factors influencing their distribution as well as detecting possible spatial and temporal evolutions, with special attention to hydrography and to global climate changes. During the ANT-XXVI/3 expedition of the icebreaking RV Polarstern in February-March 2010, 8270 seabirds belonging to 15 identified species were recorded in the Amundsen Sea during 1070 half-hour transect counts, i.e. a mean of 8 per count. The most numerous species were by far Antarctic petrel Thalassoica antarctica, Adélie penguin Pygoscelis adeliae and snow petrel Pagodroma nivea: they represented together more than 80% of the total recorded. Substantial seabird hotspots were concentrated on three icebergs, representing 44% of all observations: 85% of the Antarctic petrels and 40% of the snow petrels (Joiris[11]). Most numerous pinniped was crabeater seal Lobodon carcinophaga representing 98% of the total of 2350 individuals belonging to four species (Joiris and D’Hert[18]). Among cetaceans, the most abundant species were Antarctic minke whale Balaenoptera bonaerensis and fin whale Balaenoptera physalus (60% and 25% of the total of 170, four species). Their quantitative distribution was directly influenced by hydrological structures: water masses and fronts, pack ice and ice edge, and some free-drifting icebergs.